You can always require plaintiffs to post bond in advance. This is what is done with shareholder derivatives suits in most states. Bond requirements are undesirable in cases where meritorious plaintiffs may have no money at all, but that should not be a concern for patent cases (the idea of an "individual genius inventor" is more or less romantic mythology these days).
With the assumption that patents are worth having, that would no longer be a bad thing. The biggest problem with these trolls is that there is hardly any risk or cost in suing, and they can disengage at any point if that starts to change. This places the defendants are at a significant disadvantage.
With that inequality out of the way, patents could be what they are promised to be: a way to ensure you can monetize to recover a significant investment that you wouldn't have made without the promise of that patent.
(I don't subscribe to the idea that patents are a good thing though; especially the kind of patents that seem to make up 99% of the patent pool).